In this study, X-ray stress measurements of ferritic steel based on Fourier analysis are conducted. Taira et al. developed the cosα method for X -ray stress measurements using a two-dimensional X-ray detector. Miyazaki et al. reported that the cosα method can be described more concisely by developing the Fourier series (the Fourier analysis method). The Fourier analysis method is expected to yield the stress measurement with an imperfect Debye–Scherrer ring and there is a possibility that the materials evaluation is different compared with the conventional method, that is, the sin 2 ψ method. In the Fourier analy sis method, the strain measured by X-rays is developed as a Fourier series, and all the plane-stress components can be calculated from the Fourier series. In this study, the normal stress calculation was confirmed. In addition, the Fourier-analysis and cos α methods were used for X -ray stress measurements during a four-point bending test on a S45C test piece, and the effectiveness of the Fourier analysis method was confirmed. It was found that the experimental results from the Fourier analysis and cosα metho ds were nearly identical. In addition, the measurement accuracies of both the methods were equivalent.
{"title":"X-ray Stress Measurement of Ferritic Steel Using Fourier Analysis of Debye-Scherrer Ring","authors":"Y. Fujimoto, T. Miyazaki, T. Sasaki","doi":"10.2472/JSMS.64.567","DOIUrl":"https://doi.org/10.2472/JSMS.64.567","url":null,"abstract":"In this study, X-ray stress measurements of ferritic steel based on Fourier analysis are conducted. Taira et al. developed the cosα method for X -ray stress measurements using a two-dimensional X-ray detector. Miyazaki et al. reported that the cosα method can be described more concisely by developing the Fourier series (the Fourier analysis method). The Fourier analysis method is expected to yield the stress measurement with an imperfect Debye–Scherrer ring and there is a possibility that the materials evaluation is different compared with the conventional method, that is, the sin 2 ψ method. In the Fourier analy sis method, the strain measured by X-rays is developed as a Fourier series, and all the plane-stress components can be calculated from the Fourier series. In this study, the normal stress calculation was confirmed. In addition, the Fourier-analysis and cos α methods were used for X -ray stress measurements during a four-point bending test on a S45C test piece, and the effectiveness of the Fourier analysis method was confirmed. It was found that the experimental results from the Fourier analysis and cosα metho ds were nearly identical. In addition, the measurement accuracies of both the methods were equivalent.","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":"26 1","pages":"567-572"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84037213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, the effect of water-soluble components on the thermal fluidity of steam-treated bamboo powder was investigated. Bamboo powders were steam-treated at 180 or 200 °C for various steam treatment times. The bamboo powders were then treated with hot water to extract the water-soluble components. The flow rates of steam-treated bamboo powders that were either treated with hot water or not treated were measured using a capillary rheometer. In addition, thermogravimetry (TG) was also used to examine the differences in the thermal characteristics of bamboo powder treated by hot water extraction. The experimental results indicated that the quantity of hot water extract varied with the steam treatment temperature and time. Flow tests showed that bamboo powders not treated with hot water flowed, whereas those treated with hot water did not flow. The flow behavior and flow rate of the untreated powder became stable and high with an increase in the steam treatment time for steam treatment at 180 °C. For steam treatment at 200 °C, the flow behavior was more stable, and the flow rate became the highest by short time steam treatment. TG measurement of the powders suggested that water-soluble contains many volatile components, and the amount of volatile components changed along with the denaturation of the water soluble components. From these results, it was confirmed that not only the quantity of the water-soluble components but also denaturation of the water soluble component affects the thermal fluidity of the steam-treated bamboo powder.
{"title":"Effect of Water-soluble Components Mass on the Fluidity of the Steam-treated Bamboo Powder Caused by Heating and Compression","authors":"S. Kajikawa, T. Iizuka","doi":"10.2472/JSMS.64.381","DOIUrl":"https://doi.org/10.2472/JSMS.64.381","url":null,"abstract":"In this study, the effect of water-soluble components on the thermal fluidity of steam-treated bamboo powder was investigated. Bamboo powders were steam-treated at 180 or 200 °C for various steam treatment times. The bamboo powders were then treated with hot water to extract the water-soluble components. The flow rates of steam-treated bamboo powders that were either treated with hot water or not treated were measured using a capillary rheometer. In addition, thermogravimetry (TG) was also used to examine the differences in the thermal characteristics of bamboo powder treated by hot water extraction. The experimental results indicated that the quantity of hot water extract varied with the steam treatment temperature and time. Flow tests showed that bamboo powders not treated with hot water flowed, whereas those treated with hot water did not flow. The flow behavior and flow rate of the untreated powder became stable and high with an increase in the steam treatment time for steam treatment at 180 °C. For steam treatment at 200 °C, the flow behavior was more stable, and the flow rate became the highest by short time steam treatment. TG measurement of the powders suggested that water-soluble contains many volatile components, and the amount of volatile components changed along with the denaturation of the water soluble components. From these results, it was confirmed that not only the quantity of the water-soluble components but also denaturation of the water soluble component affects the thermal fluidity of the steam-treated bamboo powder.","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":"104 1","pages":"381-386"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85526993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Kimura, Sunhee Hong, Daiki Tanaka, Yuichi Sato, Y. Kaneko
This study investigates characteristics of drying shrinkage and creep of “Steel Chip Reinforced Cementitious Composite (SCRCC)”. Firstly, four restrained wall specimens made of normal mortar and the SCRCC with varied amount of steel reinforcing bars (4 or 10) are prepared to compare the drying shrinkage characteristics. The specimens are restrained on rigid laboratory floor so that shrinkage cracks are induced. The drying shrinkage strains are measured by contact gauge method and compared with unrestrained small specimens. Number of cracks are simultaneously observed. Secondly, creep test is carried out to improve accuracy of analysis of the drying shrinkage behaviors. Twelve block specimens are made and constant flexural load is applied for 7, 14, and 28 days. The shrinkage strains and creep strains of SCRCC are modeled by modifying CEB-FIP Model Code 1990. These models are incorporated with bond computation between SCRCC and steel bar to predict the number of drying shrinkage cracks.
{"title":"Prediction of Drying Shrinkage Cracking of Steel Chip Reinforced Cementitious Composite Considering Tensile Creep","authors":"S. Kimura, Sunhee Hong, Daiki Tanaka, Yuichi Sato, Y. Kaneko","doi":"10.2472/JSMS.64.628","DOIUrl":"https://doi.org/10.2472/JSMS.64.628","url":null,"abstract":"This study investigates characteristics of drying shrinkage and creep of “Steel Chip Reinforced Cementitious Composite (SCRCC)”. Firstly, four restrained wall specimens made of normal mortar and the SCRCC with varied amount of steel reinforcing bars (4 or 10) are prepared to compare the drying shrinkage characteristics. The specimens are restrained on rigid laboratory floor so that shrinkage cracks are induced. The drying shrinkage strains are measured by contact gauge method and compared with unrestrained small specimens. Number of cracks are simultaneously observed. Secondly, creep test is carried out to improve accuracy of analysis of the drying shrinkage behaviors. Twelve block specimens are made and constant flexural load is applied for 7, 14, and 28 days. The shrinkage strains and creep strains of SCRCC are modeled by modifying CEB-FIP Model Code 1990. These models are incorporated with bond computation between SCRCC and steel bar to predict the number of drying shrinkage cracks.","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":"27 1","pages":"628-633"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83436634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The evaluation of fatigue limit is important in designing products. The fatigue limit estimation based on dissipated energy has been getting considerable attentions. In this method, the temperature change due to irreversible energy dissipation is measured by infrared thermography for various levels of stress amplitude. It is known that the dissipated energy increases with increasing stress levels, and a certain stress level, where the change in dissipated energy shows the sharp increase, coincides with the fatigue limit of the material. In this study, the dissipated energy measurement was applied to the estimation of the crack initiation location. The fatigue limit estimation was carried out for the specimen that had multiple notches. The estimated fatigue limit showed similar value at each notch and that gave close agreement with the fatigue limit obtained from conventional fatigue tests. On the other hand, the magnitude and change of dissipated energy at each notch were different. In experiments of fatigue limit estimation, the notch, where the maximum value of dissipated energy was measured, was different from the notch where the maximum sum of principal stress was measured. To investigate the location of the crack initiation, the same specimen was carried out in the constant stress amplitude fatigue test. It was found that the notch where the largest dissipated energy was observed coincided with the crack initiated notch. Therefore, it was considered that the location of crack initiation could be estimated at the early period of fatigue by using the dissipated energy measurement.
{"title":"Estimation of Fatigue Crack Initiation Location Based on Dissipated Energy Measurement","authors":"A. Akai, K. Inaba, D. Shiozawa, T. Sakagami","doi":"10.2472/JSMS.64.668","DOIUrl":"https://doi.org/10.2472/JSMS.64.668","url":null,"abstract":"The evaluation of fatigue limit is important in designing products. The fatigue limit estimation based on dissipated energy has been getting considerable attentions. In this method, the temperature change due to irreversible energy dissipation is measured by infrared thermography for various levels of stress amplitude. It is known that the dissipated energy increases with increasing stress levels, and a certain stress level, where the change in dissipated energy shows the sharp increase, coincides with the fatigue limit of the material. In this study, the dissipated energy measurement was applied to the estimation of the crack initiation location. The fatigue limit estimation was carried out for the specimen that had multiple notches. The estimated fatigue limit showed similar value at each notch and that gave close agreement with the fatigue limit obtained from conventional fatigue tests. On the other hand, the magnitude and change of dissipated energy at each notch were different. In experiments of fatigue limit estimation, the notch, where the maximum value of dissipated energy was measured, was different from the notch where the maximum sum of principal stress was measured. To investigate the location of the crack initiation, the same specimen was carried out in the constant stress amplitude fatigue test. It was found that the notch where the largest dissipated energy was observed coincided with the crack initiated notch. Therefore, it was considered that the location of crack initiation could be estimated at the early period of fatigue by using the dissipated energy measurement.","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":"21 1","pages":"668-674"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89473778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yoshinori Yamada, M. Kitagawa, Masahito Saitou, S. Nakagawa, M. Nishijima
In our previous study, diffuse slip line (DSL) yield mode without an inhomogeneous deformation, local shear band and necking, has been found by in-situ observations of simple shear deformation for glassy polyethylene terephthalate (PET) under the conditions of low strain rates and high temperatures. Growth process of DSL can be formulated as a thermally activated process, that is, Eyring’s flow model. The growth rate and density of DSL increase with increasing stress and strain, respectively. Plastic deformation proceeds by molecular process which activated segments of polymer chains exchange their positions with free volume under applied shear stress. In the present study, several parameters necessary for an empirical simulation of stress-strain curves, that is, activation parameters, variation rate of DSL length with stress, and variation rate of DSL density with strain have been determined experimentally. Using these parameters, stress-strain curves are culculated by an analogical analysis to Johnston-Gilman’s mathematical method for the yield of metals.
{"title":"Empirical Simulation of Stress-Strain Curves for Plastic Deformation of Glassy Polymer","authors":"Yoshinori Yamada, M. Kitagawa, Masahito Saitou, S. Nakagawa, M. Nishijima","doi":"10.2472/JSMS.64.29","DOIUrl":"https://doi.org/10.2472/JSMS.64.29","url":null,"abstract":"In our previous study, diffuse slip line (DSL) yield mode without an inhomogeneous deformation, local shear band and necking, has been found by in-situ observations of simple shear deformation for glassy polyethylene terephthalate (PET) under the conditions of low strain rates and high temperatures. Growth process of DSL can be formulated as a thermally activated process, that is, Eyring’s flow model. The growth rate and density of DSL increase with increasing stress and strain, respectively. Plastic deformation proceeds by molecular process which activated segments of polymer chains exchange their positions with free volume under applied shear stress. In the present study, several parameters necessary for an empirical simulation of stress-strain curves, that is, activation parameters, variation rate of DSL length with stress, and variation rate of DSL density with strain have been determined experimentally. Using these parameters, stress-strain curves are culculated by an analogical analysis to Johnston-Gilman’s mathematical method for the yield of metals.","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":"42 1","pages":"29-35"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74459569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Report on CP2015","authors":"N. Hiyoshi","doi":"10.2472/jsms.64.1054","DOIUrl":"https://doi.org/10.2472/jsms.64.1054","url":null,"abstract":"","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":"211 1","pages":"1054"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75879440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
During tempering process of steel materials, a plastic strain occurs along loading direction even if the macro-scopic stress is less than yield stress. The authors name this phenomenon “ tempering plasticity ”. The tempering plasticity may occur by not only external force but also residual stress. It can be expected, therefore, to improve the precision of prediction of residual stress by taking account of the tempering plasticity. In this paper the plastic strain is experimentally investigated by tempering of quenched specimen under tensile or compressive stress and a mathematical model of tempering plastic strain rate is formulated by using an analogy between transformation plasticity and tempering plasticity. The newly developed formulation of tempering plasticity is implemented in commercial FE code and is applied to evaluate the residual stress after tempering in the locally quenched steel block. It is confirmed that the new model predicts the residual stress in high precision.
{"title":"High Accurate Prediction of Residual Stress Considering Plasticity during Tempering Process","authors":"Y. Yamazaki, K. Okamura, Takahisa Suzuki","doi":"10.2472/JSMS.64.266","DOIUrl":"https://doi.org/10.2472/JSMS.64.266","url":null,"abstract":"During tempering process of steel materials, a plastic strain occurs along loading direction even if the macro-scopic stress is less than yield stress. The authors name this phenomenon “ tempering plasticity ”. The tempering plasticity may occur by not only external force but also residual stress. It can be expected, therefore, to improve the precision of prediction of residual stress by taking account of the tempering plasticity. In this paper the plastic strain is experimentally investigated by tempering of quenched specimen under tensile or compressive stress and a mathematical model of tempering plastic strain rate is formulated by using an analogy between transformation plasticity and tempering plasticity. The newly developed formulation of tempering plasticity is implemented in commercial FE code and is applied to evaluate the residual stress after tempering in the locally quenched steel block. It is confirmed that the new model predicts the residual stress in high precision.","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":"11 1","pages":"266-273"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74334780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A complex stress occurs on a mechanical surface of transport machineries in service such as automobiles and railway vehicles. The authors have developed a fatigue testing machine enable to reproduce such a complex stress. The surface stress on mechanical structures can be described as in-plane structural element deformations in transverse, longitudinal and diagonal directions. The testing machine is able to reproduce stress states working on surfaces of mechanical structures by applying three independent loads to the test specimen using actuators which apply loads in the 0, 45 and 90 degree direction. The testing machine was developed with consists of a fixed frame which forms 45-degree axis and two movable frames which form 0-degree and 90-degree axes. Evaluations were conducted on the test specimen with the complex stress data obtained from an actual operating transport machinery, further it was found that the measured stress and the emulated stress corresponded with an error range of less than 10%. When additional fatigue tests were performed on a test specimen with a cylindrical projection, it was found that fatigue failure occurred at stress concentration point in the root of projection.
{"title":"Development of Planar Tri-Axial Fatigue Testing Machine for Reproducing Arbitrary Stress States","authors":"Takeshi Inoue, R. Nagao, N. Takeda","doi":"10.2472/JSMS.64.887","DOIUrl":"https://doi.org/10.2472/JSMS.64.887","url":null,"abstract":"A complex stress occurs on a mechanical surface of transport machineries in service such as automobiles and railway vehicles. The authors have developed a fatigue testing machine enable to reproduce such a complex stress. The surface stress on mechanical structures can be described as in-plane structural element deformations in transverse, longitudinal and diagonal directions. The testing machine is able to reproduce stress states working on surfaces of mechanical structures by applying three independent loads to the test specimen using actuators which apply loads in the 0, 45 and 90 degree direction. The testing machine was developed with consists of a fixed frame which forms 45-degree axis and two movable frames which form 0-degree and 90-degree axes. Evaluations were conducted on the test specimen with the complex stress data obtained from an actual operating transport machinery, further it was found that the measured stress and the emulated stress corresponded with an error range of less than 10%. When additional fatigue tests were performed on a test specimen with a cylindrical projection, it was found that fatigue failure occurred at stress concentration point in the root of projection.","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":"6 1","pages":"887-894"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81820761","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shinichiro Takai, Shosuke Fujiwara, Tatsuro Hayashi, T. Kumano
We focus on the carbon powder as a conductive material which provides new feature and added value to concrete. In this study, the electromagnetic wave shielding property of mortar with carbon powder was examined by transmission test and reflection test.Also, complex specific permittivity that indicates the electrical property of material was calculated from experimental result of transmission test. Accordingly, in the transmission test, transmission amount turned out to be decreasing along with increase of carbon powder additive rate, and electromagnetic wave shielding property was improved. It was found that presumed complex specific permittivity tends to be largeboth on real part and imaginary part, along with increase of carbon powder additive rate. Key word:Carbon powder,Mortar,Electromagnetic wave shielding,Complex specific permittivity,Transmission test, Reflection test 1 緒 言 現代社会では携帯電話や無線 LAN が爆発的に普及し たことで,我々の日常生活における様々な場面でマイク ロ波帯(2~6GHz)の電磁波が利用されている.一方で, 電磁波環境は悪化の一途をたどり,外部から侵入する電 磁波によって医療機器のトラブルが発生し,病院等の施 設では,特定空間内での電磁波利用の制限や電磁波遮へ いが求められる場合もある.もし,モルタルあるいはコ ンクリートに任意に電磁波遮へい性を付与することが できれば,本来の耐荷力を担う能力に加えて,電磁波を 制御する機能を付加することが可能になる. 筆者らは,導電性材料として炭素粉末に着目し,研究 の第一段階として炭素粉末の添加がモルタルのフレッ シュ性状に与える影響,強度や弾性係数に与える影響を 明らかにするとともに,モルタルの新機能に着目し,導 電性や電磁波に対する特性について実験的に検討して きた 1),2).ここで,炭素粉末とは,生コークスを原料と した石油精製時の残さ物である.この生コークスを焼成 すると“か焼コークス”となり,焼成温度が 1700°C 程 度の比較的高温で焼成されたものがピッチ系炭素繊維 の原料となる.これに対して 1200~1400°C で焼成,粉 砕されたものが炭素粉末となり,炭素粉末は炭素繊維原 料に比べて非晶質である. 既往の研究では,炭素繊維等の導電性を有する炭素材 料をセメントペーストやモルタルに混入し,電磁波遮へ い性や吸収性(反射減衰効果)の向上を検討している . ただし,これらの試験に用いられている配合や試験体の 含水状態に関する情報は少ない.また,従来の同軸管法 等の試験方法で測定する場合,試験体の厚さも数ミリ 程度であり,本来の構造部材としての仕様とは異なる. そこで本研究は利用頻度の高いマイクロ波帯を対象 とした電磁波遮へいを可能にする構造体コンクリート あるいは埋設型枠用モルタル等の開発を目的に,炭素粉 末を添加したモルタルを用いて実際に使用する条件に 近い試験体寸法での電磁波遮へい性など各種試験を行 い,それらの開発に必要な基礎データを収集した. 電磁波遮へい性の試験は,比較的大型の試験体におい ても測定可能な透過法 を用いて行った.また,透過法で 得られた結果を用いて,材料の電気的特性を示す複素比 誘電率の推定を行った.さらに,反射法による試験を行 い,電磁波の吸収性についても併せて評価した. 2 実験概要 2・1 使用材料 Table 1 に使用材料および使用材料の物理的性質を示 す.セメントは普通ポルトランドセメントを,細骨材に は湖底砂(琵琶湖産)を,炭素粉末は 0.3mm 以下に粉砕 したものを使用した.また,モルタル中の空気量は,電 磁波遮へい性に影響を及ぼす可能性が考えられたため, 空気量の影響を排除することを目的にすべての配合で 消泡剤を使用し,空気量が 1%以下となるように調整し た. 2・2 モルタルの配合 Table 2 にモルタルの示方配合を示す.モルタルの配合 は,水セメント比(以下,W/C)を 50%,細骨材とセメ ントの質量比 S/C=2 のモルタルをベースとして, W/C=50,60,70%の 3 水準,炭素粉末は細骨材の一部 を置換する形で内割り混入とし,炭素粉末添加率(以下, CP)をモルタルの体積比で 0~20%の範囲で変化させた. 2・3 実験項目および測定項目 試験は自由空間における遠方界の透過法および反射 法を用いた.透過法の場合,日本建築学会電磁環境小委 員会「電磁シールド材料性能測定法」 によると,試験 体取付け用開口部の周長は測定周波数の波長と同等以 上と規定している.本試験では,開口部の 1 辺を 250mm とし,300×300mm の平板試験体を用いた.したがって, 開口部周長は 1000mm となり, 1GHz 以上の波長 (λ=300mm)を用いる場合であればこの規定を満足す る.また,反射法の場合,日本建築学会電磁環境小委員 会「室内用電波吸収体性能測定法」 によると試験体の 大きさは波長の 2 倍以上と規定している.反射法に用い
{"title":"A Study on electromagnetic wave shielding of the mortar mixed with carbon powder","authors":"Shinichiro Takai, Shosuke Fujiwara, Tatsuro Hayashi, T. Kumano","doi":"10.2472/JSMS.64.1034","DOIUrl":"https://doi.org/10.2472/JSMS.64.1034","url":null,"abstract":"We focus on the carbon powder as a conductive material which provides new feature and added value to concrete. In this study, the electromagnetic wave shielding property of mortar with carbon powder was examined by transmission test and reflection test.Also, complex specific permittivity that indicates the electrical property of material was calculated from experimental result of transmission test. Accordingly, in the transmission test, transmission amount turned out to be decreasing along with increase of carbon powder additive rate, and electromagnetic wave shielding property was improved. It was found that presumed complex specific permittivity tends to be largeboth on real part and imaginary part, along with increase of carbon powder additive rate. Key word:Carbon powder,Mortar,Electromagnetic wave shielding,Complex specific permittivity,Transmission test, Reflection test 1 緒 言 現代社会では携帯電話や無線 LAN が爆発的に普及し たことで,我々の日常生活における様々な場面でマイク ロ波帯(2~6GHz)の電磁波が利用されている.一方で, 電磁波環境は悪化の一途をたどり,外部から侵入する電 磁波によって医療機器のトラブルが発生し,病院等の施 設では,特定空間内での電磁波利用の制限や電磁波遮へ いが求められる場合もある.もし,モルタルあるいはコ ンクリートに任意に電磁波遮へい性を付与することが できれば,本来の耐荷力を担う能力に加えて,電磁波を 制御する機能を付加することが可能になる. 筆者らは,導電性材料として炭素粉末に着目し,研究 の第一段階として炭素粉末の添加がモルタルのフレッ シュ性状に与える影響,強度や弾性係数に与える影響を 明らかにするとともに,モルタルの新機能に着目し,導 電性や電磁波に対する特性について実験的に検討して きた 1),2).ここで,炭素粉末とは,生コークスを原料と した石油精製時の残さ物である.この生コークスを焼成 すると“か焼コークス”となり,焼成温度が 1700°C 程 度の比較的高温で焼成されたものがピッチ系炭素繊維 の原料となる.これに対して 1200~1400°C で焼成,粉 砕されたものが炭素粉末となり,炭素粉末は炭素繊維原 料に比べて非晶質である. 既往の研究では,炭素繊維等の導電性を有する炭素材 料をセメントペーストやモルタルに混入し,電磁波遮へ い性や吸収性(反射減衰効果)の向上を検討している . ただし,これらの試験に用いられている配合や試験体の 含水状態に関する情報は少ない.また,従来の同軸管法 等の試験方法で測定する場合,試験体の厚さも数ミリ 程度であり,本来の構造部材としての仕様とは異なる. そこで本研究は利用頻度の高いマイクロ波帯を対象 とした電磁波遮へいを可能にする構造体コンクリート あるいは埋設型枠用モルタル等の開発を目的に,炭素粉 末を添加したモルタルを用いて実際に使用する条件に 近い試験体寸法での電磁波遮へい性など各種試験を行 い,それらの開発に必要な基礎データを収集した. 電磁波遮へい性の試験は,比較的大型の試験体におい ても測定可能な透過法 を用いて行った.また,透過法で 得られた結果を用いて,材料の電気的特性を示す複素比 誘電率の推定を行った.さらに,反射法による試験を行 い,電磁波の吸収性についても併せて評価した. 2 実験概要 2・1 使用材料 Table 1 に使用材料および使用材料の物理的性質を示 す.セメントは普通ポルトランドセメントを,細骨材に は湖底砂(琵琶湖産)を,炭素粉末は 0.3mm 以下に粉砕 したものを使用した.また,モルタル中の空気量は,電 磁波遮へい性に影響を及ぼす可能性が考えられたため, 空気量の影響を排除することを目的にすべての配合で 消泡剤を使用し,空気量が 1%以下となるように調整し た. 2・2 モルタルの配合 Table 2 にモルタルの示方配合を示す.モルタルの配合 は,水セメント比(以下,W/C)を 50%,細骨材とセメ ントの質量比 S/C=2 のモルタルをベースとして, W/C=50,60,70%の 3 水準,炭素粉末は細骨材の一部 を置換する形で内割り混入とし,炭素粉末添加率(以下, CP)をモルタルの体積比で 0~20%の範囲で変化させた. 2・3 実験項目および測定項目 試験は自由空間における遠方界の透過法および反射 法を用いた.透過法の場合,日本建築学会電磁環境小委 員会「電磁シールド材料性能測定法」 によると,試験 体取付け用開口部の周長は測定周波数の波長と同等以 上と規定している.本試験では,開口部の 1 辺を 250mm とし,300×300mm の平板試験体を用いた.したがって, 開口部周長は 1000mm となり, 1GHz 以上の波長 (λ=300mm)を用いる場合であればこの規定を満足す る.また,反射法の場合,日本建築学会電磁環境小委員 会「室内用電波吸収体性能測定法」 によると試験体の 大きさは波長の 2 倍以上と規定している.反射法に用い","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":"93 1","pages":"1034-1040"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82107728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Stress corrosion cracking (SCC) of extruded magnesium alloy AZ80 in 0.004wt% sodium chloride (NaCl) solution at 298K was studied by slow strain rate tensile technique. The alloy was treated with naturally or artificially aging heat treatment. The eutectoid phase was precipitated by artificially aging. The specimen was machined from different orientations. One is loaded in the transverse direction with crack propagation in the longitudinal direction (i.e., T specimen). The other is loaded in the longitudinal direction with crack propagation in the radial direction (i.e., L specimen). The strain rate was changed from 8.33×10 to 8.33×10 s. The susceptibility to SCC was evaluated by fracture energy obtained by slow strain rate tensile tests. The SCC susceptibility of magnesium alloy increased with a decrease in strain rate irrespective of heat treatment and specimen orientation. The SCC susceptibility of L specimen was higher than that of T specimen. This was related with the anisotropy in corrosion resistance. In the case of L specimen, the SCC susceptibility was not affected by heat treatment condition. On the other hand, the SCC susceptibility of artificially aged T specimen is surely higher than that of naturally aged one though the artificially aging improved the corrosion resistance. It was suggested that SCC susceptibility of magnesium alloy is related with texture orientation and distribution of eutectoid phase.
{"title":"Influence of Specimen Orientation on Susceptibility to Stress Corrosion Cracking in Extruded Magnesium Alloy AZ80","authors":"M. Nakatani, H. Abé, Koshu Hanaki, H. Uchida","doi":"10.2472/JSMS.64.655","DOIUrl":"https://doi.org/10.2472/JSMS.64.655","url":null,"abstract":"Stress corrosion cracking (SCC) of extruded magnesium alloy AZ80 in 0.004wt% sodium chloride (NaCl) solution at 298K was studied by slow strain rate tensile technique. The alloy was treated with naturally or artificially aging heat treatment. The eutectoid phase was precipitated by artificially aging. The specimen was machined from different orientations. One is loaded in the transverse direction with crack propagation in the longitudinal direction (i.e., T specimen). The other is loaded in the longitudinal direction with crack propagation in the radial direction (i.e., L specimen). The strain rate was changed from 8.33×10 to 8.33×10 s. The susceptibility to SCC was evaluated by fracture energy obtained by slow strain rate tensile tests. The SCC susceptibility of magnesium alloy increased with a decrease in strain rate irrespective of heat treatment and specimen orientation. The SCC susceptibility of L specimen was higher than that of T specimen. This was related with the anisotropy in corrosion resistance. In the case of L specimen, the SCC susceptibility was not affected by heat treatment condition. On the other hand, the SCC susceptibility of artificially aged T specimen is surely higher than that of naturally aged one though the artificially aging improved the corrosion resistance. It was suggested that SCC susceptibility of magnesium alloy is related with texture orientation and distribution of eutectoid phase.","PeriodicalId":17366,"journal":{"name":"journal of the Japan Society for Testing Materials","volume":"2 1","pages":"655-661"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89873963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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